Well, the SMPS (or flyback board) board for the CE4000 is discontinued at this time. The primary IC (125257-1, VIPer100 chip), the regulator, may still be available from Crown (TBD). If the VIPER chip is gone, it most likey took out more than just the IC and diode. Verify up to the opto device.
The diode is high speed stuff. There is also some ajusteable precision diodes (such as U3, at 2.5V) that may have been taken out.

I have ordered a couple of parts from Mouser.com to try, since it seems that the regulator just shattered. I am going to try those two bits first and see if I at least get power.

Unfortunately I am not the most electronically-inclined. I know how to muddle around a circuit board with a volt-meter, but I would have to D/L every spec sheet for every part on the dang thing. All of the rest of the parts appear undamaged - but the ones I mentioned above are definitely damaged.

Thank you for the suggestion(s). I will keep them in mind if step 1 repairs fail to rectify.

I wouldn't just replace those two blown devices and power up! You definitively have other blown parts (Murphy's law! ). It is possible to discover the defective parts with just the multimeter. I do this all the time. You should not try to power up the board without having thoroughly investigated for other faults. Hey, but that's just me!
Even if you replaced those two parts, it still might not be enough to power up the amp. If the VIPer chip doesn't power up normally, it might just blow up again! Very touchy circuit. Beware!
Also, close to 170VDC is present at the VIPer chip. That's a lot of voltage if something goes wrong!

Why don't you get in contact with your local Crown dealer, or distributor. They may still have resources to repair the 4000.
Note: I still have a lot of 4000 resources (some spare defective boards, hardware, etc), in Canada. In Canada you say? Pity! (from an old tea commercial)

On the advice of another sound guy in my AO I went by the local repair shop (not music store, Crown Authorized Warranty Service) and handed over my crippled baby. I explained what happened, what I had already done (tried replacing U2 and D2 on the side-board) and we talked about Crown and their systems and architecture and whatnot.

He was super-helpful and seemed genuinely optimistic that they could isolate and solve the problem and get my amp up and runnng again. He said the CE4000 shares little in common with the 1000 and 2000 and is more like the K series, which sounded like a "good" thing in the way he presented it.

It's going to cost me a few bucks and a few weeks, but if he can rebuild/repair it for a couple of bills and I get 5 or 6 more years out of it... I'll be pretty ecstatic.

Well, I already replaced the Vper chip. I'm thinking there are other components which have been compromised. They said they would go over it and make sure it all functions, including testing the amp under a dummy load. I gave them a "go ahead and fix it without calling me first" for anything under $200.

For what I paid for the amp over twelve years ago, considering what I've heard about these amps and their service lives, and comparing that to what it would cost me to get the cheapest comparable-power appliance (Behringer EP4000) if I can get five or sixe (or more) years out of this one with a component fix, then I will consider it money well spent.